It is well known to provide markers (taggants) and packages to the fuel industry to aid in identifying taxable vs. untaxed fractions, additive packages, brand identification, etc. Until recently, tax evaders exclusively mixed similar petroleum fractions, e.g.,. kerosene into #2 oil or heating oil into diesel fuel in order to avoid taxation. Recently, a new twist has emerged, where common solvents, e.g., xylene, toluene, naptha, etc. are being used as fuel diluents to avoid taxation.
For the supplier marker systems, this has brought about a new challenge. In the past, a number of tracer molecules such as described in U.S. Pat. Nos. 5,156,653, 5,490,872 and 5,737,871 have a pale yellow body color. Intrinsic color value of such tracer molecules was described in terms of known solid dye such as color index Yellow 56.
The slight yellow color imparted by such tracer molecules, at the application level of the tracer molecule in fuel, typically 5-50 ppm, was not considered a problem due to natural yellow coloration associated with most petroleum fractions. Consequently, these products were considered "silent" or not visibly detectable when applied in the proper manner.
Other potentially useful tracer molecules might impart a different color. For example, tracer molecules described in U.S. Pat. No. 4,209,302 imparts a purple color to petroleum fuels. However, if these molecules were used in conjunction with a petroleum dye intended to color the petroleum fuel, the color of the tracer molecule used, e.g., at a 5-50 ppm level, would be masked. In this sense, these molecules could be considered "silent" in that a potential cheater would not recognize the inclusion of the tracer molecule.
Tagging of water white solvents at the current normal dosage levels, e.g., 5-50 ppm, with colored tracer molecules imparts a definite coloration to the such solvents. This is unacceptable to the governments, solvent manufacturers and consumers of these products for a variety of reasons. Governments reject imparted color due to existing regulations for such goods requiring A.P.H.A. or Sarbolt color measurements of zero. Also, the integrity of a government sponsored program is compromised because imparting color to traditionally water white substances would immediately signal to the cheater and remove the element of surprise. The consumer would equate coloration of these products with poor quality or contamination making manufacturers adamant about maintaining current standards for body color.